The present invention relates to gating control systems for an array of thyristors in general, and more particularly to static controlled converter systems embodying such a gating control system.
Firing of thyristors in a polyphase converter system involves sequential selection of a thyristor to be fired, and proper timing with respect to the applied AC power supply, in order to establish a firing delay angle which determines a predetermined converter system output.
The firing of thyristors is caused by a pulse generator outputting a hard pulse triggered in accordance with both a signal reference which is representative of the intended delay angle and a time signal which is representative of the electrical angle on the fundamental wave of the AC power supply.
It is known to use digital techniques for the generation, in relation to the fundamental AC supply voltage, of a time wave reference and for the logic selection of the thyristor "next" to be fired. See for instance U.S. Pat. Nos. 4,017,744 of F. O. Johnson and 4,173,722 of R. L. Detering. The prior art, however, uses hardwired logic as opposed to numerical techniques for the generation of the time wave reference signal, which may be digital or analog in nature, and for the comparison between time wave reference signal and delay angle reference signal, the latter which may also be either analog or digital in nature.
With the advent of microprocessing, solid state motor drives have evolved in which a microprocessor is at the center of the system regulation and control. See for instance "Adjustable Speed AC Drives-A Technology Status Review" by Bimal K. Bose IEEE Proceedings Vol. 70, No. 2, February 1982, pp. 116-135.